<i>Synchytrium endobioticum </i>causes potato wart disease, and a number of pathotypes have been reported. Identification of pathotypes relies on a bio-assay using a set of differential cultivars as described in the EPPO Diagnostic Protocol (DP). At the moment there are four dominating pathotypes recognised in Western Europe : pathotype 1(D1), 2(G1), 6(O1) and 18(T1). In recent years the standardised set of differentials was re-evaluated in a ring test using the Glynne-Lemmerzahl method including five laboratories in three different countries (Poland, Germany, the Netherlands). For the pathotypes 2(G1) and 6(O1), in some labs the cultivars Miriam and Delcora reacted not according to the rating in the EPPO DP. Recent results of an international European project (Euphresco) showed that the cultivar Talent is suitable to replace cv Miriam (to separate pathotype 6(O1) from 18(T1)). As results from the bio-assay are only available after 6-8 weeks, a PCR test was developed to discriminate pathotype 1(D1) from the other pathotypes. Within the Euphresco-project this test was ring-tested in a test performance study (TPS) including ten labs in Europe. The results will be presented in August in the meeting in Minneapolis (results not yet available).